Lens



Search Room Patented Jan. 12, 1943 UNITED STATES PATENT OFFICE LENSMaximilian J. Herzberger and Harvey 0. Roadley, Rochester, N. Y.,assignors to Eastman Kodak Company, Rochester, N. Y., a corporation ofNew Jersey Application October 29, 1941, Serial No. 416,960

Claims.

dex of this component should be between 1.68 and 1.76 and the dispersiveindex between 43 and 58. It is also advantageous to make the frontcomponent biconvex with the radius of curvature of its rear surfacebetween 5 and 20 times that of its front surface, and to make therefractive index difference at the cemented surface in the rearcomponent greater than 0.08 as shown in Patents Nos. 2,158,178 toFrederick and Schade positive lens element, the middle one is a simpleand 2,165,328 to Aklin and Altman. biconcave lens element, and the rearone is a The accompanying drawing shows an objective doublet with itsrear surface convex and consistaccording to the invention andconstructional ing o a negative element cemented to a positive data fortwo embodiments of the invention. This element of higher index.Objectives of this type data is also given here: are widely used at anaperture of f /4.5 and some- Examplel hm mm "25 times at f/3.5 or evenf/2.7.

According to the present invention several new Lens v Rad Thicknessesfeatures of construction reduce the zonal aberrations and permit the useof greater apertures I L697 56! Rl=+634 mm 1:124 mm than theretofore,and when all the features are Ri=-535 i|=11.9. combined in the preferredform of the invention H m 53:33 81:: 11:3 the zonal aberrations are sogreatly reduced as g5fiig 5 i sif to permit the use of the objective atan aperture f of f/2.5 with a fiat field out to about 22 from the axis.25

The middle component is equiconcave or {/15 nearly so; the radius ofcurvature of its front surface is between 0.8 and 1.5 times that of itsLens v Thwknesses rear surface. In most objectives of this type it isnecessary to make one concave surface es- I 1-697 I 56.1%;:i-65g.55'0mm. 2 1 2 1 pecially strong in order tm II 1.617 36.6 R3:49.4 i=a.7 ration and astigmatism, and the high angle s of m 1 549 33.8figjiggg, 523:? mftherays'on this surface give rise to 1v 1.755 47.2R.=+49.4 n=17.4 large zonal abberations, as well as considerableovercorrection of the skew rays. The other features of the inventioneach contribute toward It W111 be noted that these ehamples embodymaking it possible to correct the aberration with all e features of they The front a more nearly equiconcave middle component, space is 2.5times and 2.7 times the rear space and when all are combined in thepreferred form espectlvell 1n two examples- The of the invention, themiddle component may be 40 face of the ddle component has a radius ofmade exactly equiconcave curvature respectwely times and times The otherfeatures which contribute toward that of the rear surface of the samecomponent. this end are as follows: The front airspace The front surfaceOf the front component has a should be between two and five times asgreat as radius of curvature espectlvely d the rear airspace. The frontsurface of the front times that of the front Surface of the middlecomponent should be weaker and the front surcomponent'- The otherfeatures according to the face of t second component stronger tinvention are apparent from the above tables. heretofore. Preferably thefront surface of the Having now explained d illustrated our infrontcomponent has a radius of curvature be- Vention. We W sh to point outthat it is not limited tween 0.5 f and f where f is the focal length ofthe Specific examp Shownthe objective, or between one and two times theWhat we claim is: radius of curvature of the front surface of the APhotographic Objective of the t p onsecond component. A high refractiveindex and ing of three airspaced c po nts 01 which a high dispersiveindex especially in the front e front one is a simp e pos t v lens e e et. component is advantageous. The refractive inthe middle one is a simave lens elecomponent being longer but not more than twiceas long asthat of the front surface of the second component.

2. An objective according to claim 1 in which the front component has arefractive index between 1.68 and 1.76 and a dispersive index between 43and 58.

3. An objective according to claim 1 in which the front component isbiconvex, and the radius of curvature of its rear surface is betweenfive and twenty times that of its front surface.

4. A photographic objective of the type conslstlng of three airspacedcomponents of which the front one is a simple positive lens element, themiddle one is a simple biconcave lens element, and the rear one is adoublet with its rear surface convex and consisting of a negativeelement cemented to a positive element of higher index, characterized bythe airspace between the front and the middle component being greaterthan twice and less than flve times that between the middle and the rearcomponent, by the front surface of the middle component having a radiusof curvature between 0.8 and 1.5 times that of the rear surface of saidcomponent, and by the radius of curvature of the front surface of thefront component being between 0.5 f and f where f is the focal length ofthe objective.

5; An objective according to claim 4 in which the front component has arefractive index between 1.68 and 1.76 and a dispersive index be tween43 and 58.

MAXIIJILIAN J. HER-ZBERGER. HARVEY O. HOADLEY.

